Study Questions:

How can the prediction of cardiac complications among pregnant women with heart disease be improved?

Methods:

Two well-established Canadian centers for maternal cardiac disease prospectively collected data on pregnancies with follow-up through 6 months post-partum. Adverse events and temporal trends were assessed. Univariate and multivariate analyses of clinical and process of care variables were performed. The new risk index (CARPREG II [Cardiac Disease in Pregnancy Study]) was compared to prior risk prediction models.

Results:

Of 1,938 pregnancies, cardiac complications occurred in 16% and were primarily related to heart failure and arrhythmias. The rate of pulmonary edema decreased over time. Ten predictors of complications were identified and assigned a weighted point score in the new CARPREG II risk index: 3 points for prior cardiac events or arrhythmias, baseline New York Heart Association (NYHA) functional class III/IV or cyanosis, and mechanical valve; 2 points for systemic ventricular dysfunction, high-risk valve disease/left ventricular outflow tract obstruction, high-risk aortopathies, pulmonary hypertension, and coronary artery disease; and 1 point for no prior cardiac interventions and late pregnancy assessment. The new CARPREG II risk index has five categories based on the sum of points, each with an associated risk of cardiac complications: 0-1 point (5%); 2 points (10%); 3 points (15%); 4 points (22%); and more than 4 points (41%). CARPREG II had a C-statistic of 0.78 (95% confidence interval, 0.73-0.83), which was higher than the original CARPREG, ZAHARA, and mWHO methods of risk prediction.

Conclusions:

Among women with heart disease, risk of adverse cardiac events during pregnancy can be predicted by utilizing a variety of clinical, lesion-specific, and process-of-care variables.

Perspective:

When the original CARPREG I risk prediction score was published in 2001, the field of maternal cardiac care was transformed. Since that time, additional studies have looked at ways to calculate risk, including those focused specifically on lesion-specific conditions. In this study, CARPREG II further advances and improves our ability to predict risk by using a combination of factors.

In addition to offering superior risk prediction capability, this study also raises several other important issues to consider. First, this study was conducted at two highly specialized multidisciplinary centers in Canada that focus on the care of women with cardiac disease. More centers like this are needed. Second, cardiac complications related to pregnancy can occur up to 6 months post-partum, but in the United States, many women lose their medical insurance after only 6 weeks post-partum. Third, women presenting late in pregnancy for assessment (>20 weeks gestation) had an increased risk of complications. Delays in referral and access to specialized care need to be addressed. Fourth, even women in the lowest risk group had 5% risk of cardiac complications, further reinforcing the need for specialized centers to care for these women. Last, many women with high-risk cardiac disease would have been under-represented in this study by means of having been counseled against pregnancy. Like all risk prediction tools, this score needs to be tailored to the individual patient and interpreted by a medical team with experience managing pregnant women with complex cardiac disease.